In today's communication, radio frequency (RF) modulation protocols have increased in complexity. Therefore, the process of making the communications more accurate has accordingly become more complex. In the past, the time and effort required to implement the necessary hardware and software to accomplish this extended accuracy has been very large. RF signals which have been down converted to a baseband frequency range have been historically comprised of single complex electrical signals, where complex entails two types of data embedded therein, real and imaginary. These signals have been called IF in nature because they represent data in the intermediate frequency range. A direct conversion of the IF waveform into two separate real signals is becoming the normal practice. These two signals are commonly called the “I” for in phase and the “Q” for in quadrature. “In quadrature” refers to the signal being 90 degrees out of phase. The motivation to convert single, complex IF waveforms into two real waveforms stems from the fact that two digital to analog converters (DAC) operate at twice the speed of a single DAC. These will double the possible data transmission rate of the communication and increase the accuracy of the transmission fidelity. Because of this advantage, single signal, complex IF intermediate stages are disappearing. However, one requirement of I and Q arbitrary waveform generators (AWG) and digitizers (DGT) is that they be highly balanced in phase and magnitude relative to each other. This is a difficult practice, time intensive, and costly to achieve.
Historically, the requirement to achieve balanced I and Q signals has challenged automatic test equipment (ATE) since such a balance is frequency and magnitude dependent. In order to calibrate out the frequency response of the I and Q paths, calibration at each tone frequency must occur. However, it is nearly impossible for a system calibration procedure to calibrate an ATE at all possible frequencies as the number involved is infinite. A more tractable approach is to calibrate at only those frequencies and amplitudes to be used by a given test program performed by the ATE. Conventional systems and software have been upgraded to enable users to accomplish this using a new Application Programming Interface (API), new additions to the analog calibration menu, and a new calibration load board. Nevertheless, efficiency problems still occur, in particular with regard to a number of relays required on the load board.